The present invention relates to apparatus for reclaiming industrial effluent water, i.e., acid-alkali effluent water containing organic matter, and more particularly to apparatus for reclaiming effluent water containing ammonia and organic matter at relatively low concentrations, fluorine as the case may be, and further phosphoric acid, especially the effluent water to be discharged from the wet process practiced with use of ultrapure water in plants for manufacturing semiconductors, liquid crystals or like electronic products or devices.
When acid-alkali effluent water containing several ppm of organic matter is to be reclaimed, the effluent water is first neutralized in a neutralizing tank and thereafter treated in a biological treatment tank to decompose and remove the organic matter as shown in FIG. 3. The biologically treated water is subsequently supplied to an ultrafiltration (UF) circulation tank and then to a UF device to remove an SS component consisting mainly of microorganisms and contained in the treated water. The biologically treated water resulting from the removal of SS is fed to a regenerative ion exchange device for the removal of inorganic ions. The treated water free from inorganic ions is reused as recycled water from waste water or water for replenishing a cooling tower.
In the flow chart of FIG. 3, each reference numeral stands for as follows.
51; collected effluent
52; neutralizing agent
53; oxygen dissolving tank
54; UF circulation tank
55; air
56; regenerative ion exchange device
The other reference numerals are the same as those of FIG. 1.
In the case of fluorine-containing effluent water, slaked lime is first added to the collected effluent water in a reactor for the primary treatment of the effluent water as shown in FIG. 4. CaF2 is formed according to the reaction formula:
Ca2+2Fxe2x88x92xe2x86x92CaF2
to precipitate in a settling tank, and sludge containing the precipitate is removed with a dehydrator. On the other hand, the water resulting from the primary treatment is treated in a biological treatment tank to decompose and remove organic matter. Aluminum sulfate serving as a coagulant is further added to the biologically treated water in a reactor for advanced treatment. Al(OH)3 having a fluorine adsorbing property and formed according to the reaction formula:
Al3++3OHxe2x86x92Al(OH)3
is caused to adsorb the fluorine, followed by precipitation in a settling tank. The resulting sludge containing the Al(OH)3 is removed with the dehydrator. The fluorine contained in a very small amount in the water subjected to the advanced treatment is removed by adsorption in a adsorption column packed with a chelate resin. The water treated is discharged from the column.
In the flow chart of FIG. 4, each reference numeral stands for as follows.
61; flourine-containing collected effluent
62; slaked lime
63; settling tank
64; dehydrator
65; aluminum sulfate
66; sludge
67; discharge
The other reference numerals are the same as those of FIG. 1.
The apparatus for reclaiming acid-alkali effluent water containing several ppm of organic matter includes a regenerative ion exchange device as described above. This device requires regeneration of the resin when ions are adsorbed to saturation. Usually 2 or 3 equivalent weights of a regenerant is used for removing one equivalent weight of ions and discharged from the device, while the regeneration discharges a large quantity of effluent. This gives rise to a need to suitably treat the effluent additionally.
The apparatus for reclaiming effluent water containing organic matter develops troubles such as clogging of the separation membrane device or ion exchange device disposed at a downstream location because the organic matter in the collected effluent permits active growth of microorganisms or because the metabolites of microorganisms, or fungi will leak.
On the other hand, slaked lime for use in treating fluorine-containing effluent water is in the form of fine particles and produces fine particles of CaF2 through a liquid-phase reaction when dissolved in water. For a further advanced treatment of the effluent water, there is a need to add a coagulant to the water. The sludge produced by the use of these chemicals must be separated off by equipment such as a coagulation tank and thickener. The equipment then requires a large area for installation. To reduce the fluorine concentration of the treated water below the effluent regulation level, slaked lime serving as a neutralizing agent, aluminum sulfate as a coagulant, high-molecular-weight coagulant, etc. need to be used in excessive amounts, consequently producing a large quantity of sludge and adding to the amount of waste to be discarded. The sludge contains about 80% of water even when dewatered, and the CaF2 content of the sludge is usually up to 10%.
The water recovered still remains to be treated for use as the raw water to be supplied to the pure water system resorting to conventional ion exchange and membrane separation.
An object of the present invention is to provide a compact effluent water reclamation apparatus which is minimized in the kinds and amounts of chemicals to be used for the recovery of water to thereby reduce the amount of waste and eliminate equipment, such as a thickener, which necessitates a large area for installation.
Another object of the invention is to provide an effluent water reclamation apparatus which is adapted for continuous treatment free of the likelihood of a membrane separation device or ion exchange device becoming clogged with microorganisms.
The present invention provides a first effluent water reclamation apparatus comprising a reverse osmosis device and adapted to treat acid-alkali effluent water containing organic matter but no fluorine. The first apparatus concentrates acid-alkali effluent water containing organic matter by reverse osmosis, evaporates the resulting concentrated water to dryness and collects the water permeating through a reverse osmosis membrane. The apparatus is characterized in that the apparatus comprises as arranged upstream from the reverse osmosis device a neutralizing device for neutralizing the effluent water to prevent a scale component from separating out from the effluent water in the process of reverse osmosis, and a biological treatment tank for biologically treating the neutralized effluent water.
With the first effluent water reclamation apparatus, fluorine-free effluent water is neutralized, for example, with an aqueous solution of caustic soda at a position upstream from the reverse osmosis device so as to render the effluent water unlikely to permit a scale component to separate out (to give high solubility) even if the water is concentrated to an extreme extent with the reverse osmosis device. The neutralized effluent water is treated in the biological treatment device to decompose and remove the organic matter. The biological treatment tank has an activated carbon packed layer which is fully supplied with oxygen or which is fluidized while being supplied with oxygen. Ammonia is digested in the biological treatment tank when contained in the effluent water. The pH of the effluent water drops during the process of digestion, so that the water is neutralized with an aqueous solution of caustic soda. The treated water flowing out from the biological treatment tank contains an SS component consisting predominantly of bacterial cells, so that the SS component is removed with an ultrafiltration (UF) device. The ultrafiltration (UF) membrane to be used is one having special spacers adapted to prevent adhesion of or clogging with bacterial cells, such as Preprox UF membrane, product of Kurita Water Industries, Ltd. Alternatively available is a method of conducting the biological treatment and removing the SS component in a single tank, by immersing a microfiltration (MF) membrane in a biological treatment tank wherein an activated carbon layer is fluidized with a supply of oxygen and sucking the effluent water through the MF membrane to obtain permeating water. The biologically treated water resulting from the removal of the SS component has high solubility and can therefore be concentrated with a reverse osmosis (RO) device to an extreme extent, for example, to {fraction (1/40)} of the amount of treatment (permeating water 97.5, concentrated water 2.5 when the amount of treatment is taken as 100). The reverse osmosis (RO) membrane is, for example, SE-10, product of Nitto Denko Corp. The water concentrated to an extreme extent is fed to an evaporator-dryer, whereby the sludge component is evaporated to dryness. The evaporator-dryer is, for example, a drum dryer. The water permeating through the reverse osmosis membrane is collected for reuse as recycled water from waste water, water for replenishing a cooling tower or raw water for the distillation pure water system.
The present invention provides a second effluent water reclamation apparatus comprising a reverse osmosis device and adapted to treat acid-alkali effluent water containing fluorine in addition to organic matter. The second apparatus concentrates acid-alkali effluent water containing organic matter and fluorine by reverse osmosis, evaporates the resulting concentrated water to dryness and collects the water permeating through a reverse osmosis membrane. The apparatus is characterized in that the apparatus comprises a neutralizing device disposed upstream from the reverse osmosis device for neutralizing the effluent water to prevent a scale component from separating out from the effluent water in the process of reverse osmosis, a biological treatment tank for biologically treating the neutralized effluent water, a calcium chloride adding device for adding calcium chloride to the concentrated water resulting from the reverse osmosis, and an adsorption column for removing fluorine ions from the water permeating through the reverse osmosis membrane.
The effluent water to be treated with the second apparatus can further contain phosphoric acid.
The fluorine-containing effluent water is treated by the second apparatus in the same manner as the fluorine-free effluent water until it is treated with the reverse osmosis device for concentration. A reactor is disposed upstream from an evaporator-dryer for adding CaCl2 to the concentrated water therein. Thus added to the water concentrated in the reverse osmosis device to an extreme extent is an aqueous solution of calcium chloride in an amount approximately equivalent to the fluorine concentration. The fluorine contained in the concentrated water is converted into CaF2 of low solubility in the reactor, and the CaF2 produced is supplied to the evaporator and subjected to evaporation to dryness along with other sludge component. The conversion of the fluorine in the form of NaF as contained in the concentrated effluent water into CaF2 assures a facilitated drying procedure and ease of handling of the dried sludge. On the other hand, disposed downstream from the reverse osmosis device is an adsorption column packed with an adsorber for removing fluorine from the water permeating through the reverse osmosis membrane. The adsorber is, for example, a chelate resin or zirconium adsorber. The permeating water having the fluorine adsorbed by the chelate resin for removal is collected and reused as recycled water from waste water, water for replenishing the cooling tower or raw water for the distillation pure water system.
The biological treatment tanks for use in the first and second effluent water reclamation apparatus are preferably those for practicing the fluidized-bed biological activated carbon process. A microfiltration (MF) membrane can be provided in the treatment tank for separating the SS component from the treated water before feeding to the reverse osmosis device.
The present invention provides a third effluent water reclamation apparatus comprising an evaporator and adapted to treat acid-alkali effluent water containing organic matter but no fluorine. The third apparatus concentrates acid-alkali effluent water containing organic matter by evaporation, evaporates the resulting concentrated water to dryness and collects the vapor in the form of water. The apparatus is characterized in that the apparatus comprises as arranged upstream from the evaporator a neutralizing device for neutralizing the effluent water to prevent a scale component from separating out from the effluent water in the process of concentration by evaporation, and a biological treatment tank for biologically treating the neutralized effluent water.
The third apparatus and the treatment procedure thereof are basically the same as those of the first apparatus except that the reverse osmosis device of the first apparatus is replaced by the evaporator. With the third apparatus, the device positioned downstream from the biological treatment tank and upstream from the evaporator is mainly operated with heating and is free of troubles due to the presence of microorganisms. Accordingly an SS separator is disposed downstream from the biological treatment device for separating the SS component from the treated water. The SS separator is preferably a centrifugal strainer, which is, for example, one manufactured by IM Corporation. Examples of useful evaporators are a multi-effect evaporator and a thermo-compression evaporator.
The present invention provides a fourth effluent water reclamation apparatus comprising an evaporator and adapted to treat acid-alkali effluent water containing fluorine in addition to organic matter. The fourth apparatus concentrates acid-alkali effluent water containing organic matter and fluorine by evaporation, evaporates the resulting concentrated water to dryness and collects the vapor in the form of water. The apparatus is characterized in that the apparatus comprises a neutralizing device disposed upstream from the evaporator for neutralizing the effluent water to prevent a scale component from separating out from the effluent water in the process of concentration by evaporation, a biological treatment tank for biologically treating the neutralized effluent water, and a calcium chloride adding device for adding calcium chloride to the concentrated water resulting from the process of concentration by evaporation.
The fourth apparatus and the treatment procedure thereof are basically the same as those of the second apparatus except that the reverse osmosis device of the second apparatus is replaced by the evaporator. With the fourth apparatus as in the third apparatus, the device positioned downstream from the biological treatment tank and upstream from the evaporator can be a centrifugal strainer for removing the SS component, and the evaporator to be used is, for example, a multi-effect evaporator or thermo-compression evaporator.
The biological treatment tanks for use in the third and fourth effluent water reclamation apparatus are preferably those for practicing the fluidized-bed biological activated carbon process. A microfiltration (MF) membrane can be provided in the treatment tank for separating the SS component from the treated water before feeding to a reverse osmosis device. When required, an adsorption column is provided in the fourth apparatus for removing fluorine ions from the water permeating through the reverse osmosis membrane.
The water obtained by the treatment in the first, second, third or fourth apparatus can be collected and mixed with replenishing industrial water or city water for use as raw water for the distillation pure water system.